Answer: The most common reason for lack of flowering in the bigleaf hydrangea varieties is unfavurable weather. Since bigleaf cultivars such as your Nikko flower primarily on the previous year's growth, severe weather conditions that damage the young growth of the plant can reduce flowering. Damaging weather conditions include early fall freezes that occur before the plant is completely dormant, extremely low winter temperatures and late spring frosts that occur after the plant has broken dormancy. Late spring damage is most common, particularly in areas where see-saw temperatures are common in the spring.
You may be able to protect plants from weather-related flower bud damage by covering them. There also is evidence that some bigleaf hydrangea cultivars such as Endless Summer have the ability to flower on current year's growth, which means that, even if the plant is killed back to the ground, it should still flower during the subsequent summer. The bottom line is that moving your plant won't change its ability to flower. You'll have to rely on favorable weather for that to happen.
As for your clematis, once you have determined the clematis has wilt and has sustained permanent damage, remove all the damaged leaves and stems including those that have fallen. Be extremely careful not to injure any delicate stems that are still viable, especially at the base of the plant. After cleaning it up, make sure it is thoroughly watered.
As a precaution, a systemic fungicide should be applied in early spring before the new leaves emerge, monthly throughout the growing season and again in the fall after you have cleaned up the fallen leaves. Make sure it stays well-watered, especially during the hot, stressful parts of the season. In sandy well-drained soils, fertilize clematis with a water-soluble food every 2-3 weeks from spring until mid-August. In heavier soils, either fertilize less often (every 3-4 weeks) with an all-purpose granular garden fertilizer such as a bloom promoting 10-20-10.
Best wishes with your garden!
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